docs: small changes based on review

docs/membership-fee-overview.md

@@ -82,7 +82,6 @@ This document provides a comprehensive overview of the Membership Fees system. I
 - amount (Decimal) - Membership fee amount in Euro
 - interval (Enum) - :monthly, :quarterly, :half_yearly, :yearly
 - description (Text, optional)
-- timestamps
 ```
 
 **Important:**
@@ -101,7 +100,6 @@ This document provides a comprehensive overview of the Membership Fees system. I
 - status (Enum) - :unpaid (default), :paid, :suspended
 - amount (Decimal) - Membership fee amount at generation time (history when type changes)
 - notes (Text, optional) - Admin notes
-- timestamps
 ```
 
 **Important:**
@@ -169,11 +167,16 @@ value: UUID (Required) - Default membership fee type for new members
 
 **Algorithm:**
 
+Lock the whole cycle table for the duration of the algorithm
+
 1. Get `member.membership_fee_start_date` and member's membership fee type
-2. Calculate first cycle based on `membership_fee_start_date`
-3. Generate all cycles from start to today (or `left_at` if present)
-4. Skip existing cycles
-5. Set `amount` to current membership fee type's amount
+2. Generate cycles until today (or `left_at` if present):
+    - If no cycle exists:
+      - Generate all cycles from `membership_fee_start_date`
+    - else:
+      - Generate all cycles from last existing cycle
+    - use the interval to generate the cycles
+3. Set `amount` to current membership fee type's amount
 
 **Example (Yearly):**